Recently, environmental problems such as global warming have emerged and regulations on an exhaust gas have been strengthened.
In particular, strict standards for an exhaust amount of an automobile exhaust gas are applied in actual circumstances.
Therefore, a technique to reduce a harmful material of the vehicle exhaust gas has been developed, for example, there is an exhaust gas recirculation (EGR) apparatus.
This exhaust gas recirculation apparatus reticulates a part of the exhaust gas exhausted from the engine into the intake line, thereby having a function reducing an oxygen amount in a mixture, reducing an exhaust amount of the exhaust gas, and reducing a harmful material in the exhaust gas.
Further, the exhaust gas recirculation apparatus includes a cooler cooling the exhaust gas.
In this case, the cooler has cooling water passage through which cooling water passes and a tube through which the exhaust gas passes.
The cooler functions as a kind of a heat exchanger that performs heat exchange between the exhaust gas and the cooling water so as to prevent an excess gas temperature rising in the exhaust gas.
These coolers may be made of an aluminum alloy material of which heat transfer efficiency formed by the exhaust gas is high a formability is good.
However, in the cooler according to a conventional art, there is a problem that a penetration hole is generated in the tube vulnerable to the corrosion by corrosion ions such as Cl—, SO42-, NO3-, etc. contained in a condensed water component.
There is a problem that a leakage phenomenon of the exhaust gas occurs through the penetration hole and a cooler efficiency is deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.